How do you know for sure if a LAKE IN YOUR NEIGHBORHOOD is NATURAL or MAN MADE?

Question

my parents ar e having an arguement about it and id like to know.....is there a website where i could find this information?

Answer 1

That is a great question.

Man Made: Man made lakes usually have a "man-made" dam which holds run-off water from rivers, streams, and creeks. Dams are made to store water, for hydroelectric power production, to prevent erosion, and to make roadways. Smaller man made ponds are constructed by digging and placing some type of liner at the bottom to hold the water. The source of the water may vary.

Man made ponds and lakes are usually filled with accumulated water from a natural source such as rain, springs, streams, but not always. Water can be pumped from wells to fill a pond.

Rodent Dams: The smallest natural dams are made by beavers, but the dam allows the natural flow of downstream water. The beaver dams usually form shallow ponds and marsh like conditions near a forest.

Geologic Lakes: Natural dams form lakes too. Natural dams are the consequence of landslides, ice accumulation of glaciers, or obstructions, but they are usually impermanent. Eventually the dam material will erode and the waterway will resume natural flow.  

Volcano Lakes: Volcanoes form more permanent natural lakes. Lava flows may create lakes by blocking a canyon. Lakes also form in the craters of volcanoes during dormant periods. I think the most beautiful lakes are crater lakes with an island in the middle. Amazingly other volcanic processes beneath the earth form lakes at the surface. Super volcanoes may erupt with great ferocity leaving a huge void beneath the mountain which soon after collapses leaving a great depression at the surface which fills with water forming a lake. Clear Lake in California was formed as such.

Glacial Lakes: Other natural lakes in Minnesota were formed by the erosive process of glaciers during the ice age. The earth was gouged and displaced by the moving ice sheets. These sheets were hundreds of feet deep. When the glacier receded depressions in the ground filled with water becoming lakes. Because the topography is so level in Minnesota and  the substrate beneath the lake holds water, the water had nowhere to flow and the lakes remained.  Scientists believe the Great Lakes were formed principally by ice age glaciers.

During the Ice age glaciers themselves held vast lakes in the North American regions. A mountainous mass of ice formed a barrier dam holding back the melt waters. The lake would reach a critical level hundreds of feet deep eventually accumulating enough pressure to cause the dam to fail.   These lakes went through times when the entire lake would burst. The lake may empty completely within hours, creating gigantic floods causing devastation over huge areas.

Cosmic Lakes: A natural lake may be formed by the impact crater of a comet, or meteor.

Plate Tectonic Lakes: Lakes are also formed by tectonic processes. Large land masses move in relation to other land masses. If they oppose then uplifting may occur changing the topography and forming lakes. The land masses may separate leaving deep trenches which fill with water. A tectonic land mass may slide into position restricting continental water flow. San Francisco Bay is almost an example of this. The Pacific Plate at the San Andreas Fault moving  north may one day impede the water flow from the North American Plate thus turning the SF Bay into a lake.

Once a Gulf of Mexico oceanic bay, Lake Pontchartrain was formed by the Mississippi River Delta surrounding the mouth of the bay with sediments.  This is an example of a lake formed by deposition of sediments from waterways. Sediments are also deposited by glaciers creating moraine dammed lakes.

Erosional Lakes: High mountain lakes are formed by the action of glaciers digging out hollows called drumlins. Glacial Lake is an example. Eroded ravens and canyons may become natural lakes. The Grand Canyon was once blocked by volcanic activity forming a lake.

Spelunker Lakes: One more, I almost forgot. Underground caverns also collapse at the surface leaving holes in the ground which fill with fresh water. These lakes are the most amazing of all. Cavern lakes come in many forms. Some cavern lakes are subterranean and reach over vast regions with connecting networks of cave tunnels.  There are also completely subterranean lakes, not exposed at the surface, under ground caves which filled with water.

Indicators: To answer your question, "How do you know?", more accurately  there may be indicators. Sometimes there are indigenous lifeforms living in the lake which may indicate the age of the lake. Humans have been in the Americas for only 30 to 15 thousand years, and the industrial age ,when most man made lakes were formed, started after the 1600's, only four hundred years. The Great Salt Lake can not be man made, but the salt flats of the San Francisco Bay are man made by converting shallow salt water marsh into salt ponds by building dikes and restricting natural water flow of fresh water and salt water tides.

Man made lakes are often stocked with non-native fishes. If for example the lake has a municipality which protects native fishes from introduced species, then very likely the lake is natural.

Exceptions: A natural lake with varying seasonal water levels may be later occupied by humans and improved to allow control of the water level or increase the lake capacity. What may appear as a man made lake may be actually an ancient natural lake.

Accidental Lakes: Less common man made lakes are accidental. Lakes formed by open pit mining. If the pit reaches a water aquifer by accident and the water flow is enormous, the entire pit may fill with water forming a lake, ending the mining operation and submerging very expensive mining equipment.

I might have missed a few.

Please name  the lake under question. We can Google earth the lake to see how it was formed and end the argument.

That would be fun.

Keep asking great questions.

Answer 2

Is there a dam? If so the lake is most certainly not natural or is much bigger than it was as a natural lake.

As a rule of thumb,any lake outside New England, the Upper Midwest, and the mountainous parts of the Eastern and Western US is probably not natural. Virtually all of the lakes in states south of Pennsylvania, except for a few in the mountains, and west to the Rockies is not natural. A number of the lakes in New England, the Upper Midwest, and the mountains are also artificial, so just because the lake is in Minnesota does not mean it is natural, just more likely to be natural than a lake in, say, Georgia.

As for websites, there is not one that would answer the question, but there areones that you can look up secific lakes.

Answer 3

Look for old maps of the area - and see if the lake is in the pictures.